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Date:      Wed, 4 Jul 2001 01:55:49 -0700 (PDT)
From:      Matthew Jacob <mjacob@feral.com>
To:        Bruce Evans <bde@zeta.org.au>
Cc:        Greg Lehey <grog@FreeBSD.org>, Lars Fredriksen <lars@FreeBSD.org>, cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org
Subject:   Re: cvs commit: src/sys/cam/scsi scsi_sa.c
Message-ID:  <Pine.BSF.4.21.0107040152040.8572-100000@beppo>
In-Reply-To: <Pine.BSF.4.21.0107041846230.47446-100000@besplex.bde.org>

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On Wed, 4 Jul 2001, Bruce Evans wrote:

> On Mon, 2 Jul 2001, Greg Lehey wrote:
> 
> > On Monday,  2 July 2001 at  9:39:18 -0700, Lars Fredriksen wrote:
> > > lars        2001/07/02 09:39:18 PDT
> > >
> > >   Modified files:
> > >     sys/cam/scsi         scsi_sa.c
> > >   Log:
> > >   Reviewed by:	 Matthew Jacob
> > >   Changed the timeout to wait for writing of filemarks to complete from 1
> > >   minute to 3 minutes. This should probably be enhanced to be a sysctl variable.
> > 
> > Shouldn't this be a function of the tape drive?
> 
> Of course.  sysctl() is not very suitable for controlling devices.


The amount of time to wait for an operation to complete is a function of
a specific device (and type of media too). The means of controlling that
specific device's timeout may either be achieved with existing ioctl
mechanism (expanded mtio, e.g.), sysctl (as has been suggested), or some
other mechanism (new ioctl, other).

There already are a lot of other device 'quirks' that need to be
passed to the device driver. The current practice of compiling device
quirks is absurd. I have old mail from Mike Smith (about two years old
now) about how to start using the hint mechanism for this. This is
probably where the device timeout should go.

However, sysctl is a good choice for dynamically tunable ad hoc
variables- e.g. 'number of retries' for scsi_da.

-matt



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